This invention relates to turbo-charger systems and turbo-charged engines.
A typical turbo-charger system includes a turbine shaft having an exhaust turbine at one end that is driven by exhaust gases from the engine cylinders, and having a compressor at the other end for providing compressed air to the engine. At very high engine loads, the engine may become overcharged and/or overheated, which can be prevented by reducing the inlet air pressure supplied by the compressor turbine. One commonly used method involves the use of an exhaust waste gate connected to the exhaust gas outlet of the engine for extracting some gas directly into the atmosphere instead of by way of the exhaust turbine, to reduce the speed of the compressor. However, such a valve must be made resistent to corrosion from high temperature exhaust gases, and even so is subject to clogging. It may be noted that the exhaust turbine does not tend to clog, probably because of its high speed rotation. Another approach is to utilize a constricter valve in line with the engine air inlet, to reduce the amount of air flow towards the cylinder. However, a constricter increases the back pressure on the compressor, so that the exhaust turbine turns slower. The slower speed of the exhaust turbine results in a higher back pressure for the engine cylinder which reduces efficiency. Still another approach is to utilize a venting air valve on the downpath side of the compressor, to merely vent excessive air into the atmosphere. This approach cannot be utilized where a carburetor is stationed up-path from the compressor, since a valve would exhaust fuel into the atmosphere, which would be dangerous. This venting valve approach can be utilized with fuel injection engines only, and has been known to run turbocharger impellers at dangerously high operational speeds, sometimes causing turbocharger over speeding.
In addition to the above drawbacks of present systems, there is the problem of poor engine response while shifting gears. During rapid acceleration, there is typically a high engine load immediately before the shift, and during the shift there is a momentary closing of the throttle while the turbines lose speed. When the throttle is opened again, it requires a moment for the turbines to pick up speed to supply enough compressed air for rapid acceleration in the new gear. A turbo-charger system which could be utilized on both carburetor and fuel injection engines, which provided high engine efficiency, and which provided good engine response during gear shifting, would be of considerable value in engine design.